``The fool hath said in his heart, There is no God.'' (Ps. 14:1, KJV)





by Doug Ward

A baby chick pecks a gaping hole in the theories of those who deny the existence of a Creator.

When I was growing up, I spent many hours at the chicken hatchery owned by my mother's parents, who lived right next to us near Wooster, Ohio. There were a number of chores to do as Grandma prepared for each week's hatch. I especially remember the hours spent folding together and stapling the cardboard boxes in which the baby chicks were shipped to farmers who had ordered them.

Monday was hatching day. Every Monday morning, right on schedule, hundreds of chicks emerged from their eggs and filled the air in and around the hatchery with piles of yellow fuzz and loud ``cheep, cheep, cheeps.'' Customers arrived, and children's eyes lit up as they peeked into the boxes and saw the newly-hatched Rhode Island Reds, Barred Plymouth Rocks, and the bright yellow chicks that Grandma had named Ohio Beauties.

As the years went by, I didn't spend too much time wondering about the details of the process that led to the baby chicks' sudden appearance after exactly three weeks in the incubator. I associated the hatchery with repetitious tasks, to be completed quickly so that I could get back to books and baseball games. Still, Grandma gave my brother and me regular reminders of some of the wonderful things that were quietly going on inside the eggs that filled the big incubators. For example, she would often pick up a new baby chick and point out the sharp bump (called an ``egg tooth'') on its beak, explaining that God had provided the chick with this temporary special tool so that it could break through its shell. I mentally filed away such information for future reference.

Later, as a college student, I stumbled across an article in Scientific American [1] that describes the ways in which eggs are carefully designed to provide for all the needs of the baby birds inside them. When I first read that magazine, I was amazed to learn that what Grandma had taught us was only a small part of a much bigger picture. During the twenty years since then, I have occasionally reread the magazine and found renewed inspiration in the facts presented there.

In this article, I would like to share with you the awesome story of the wonders contained in a hen's egg. This story graphically illustrates the words written by the apostle Paul in Romans 1:20 (KJV): ``For the invisible things of him from the creation of the world are clearly seen, being understood by the things that are made, even his eternal power and Godhead....''


The Shell Game

A baby chick growing up inside of an egg obtains the energy it needs from the fat stores of the egg yolk. As this fat is burned, water is produced. The chick also takes in oxygen and discharges carbon dioxide, even before its lungs have developed. But how does oxygen reach the chick, and how do carbon dioxide and water escape from the egg?

It turns out that an eggshell contains thousands of microscopic pores-about 10,000 for a typical chicken egg. The egg admits oxygen and releases carbon dioxide through these pores by the process of diffusion, the tendency for a high concentration of one type of molecule to flow to a place where there is a lower concentration of that type of molecule. Because there is more oxygen in the air outside the eggshell, oxygen enters the egg; and because there is more carbon dioxide and water vapor inside the shell, these gases leave the egg. According to [1], ``the molecular traffic through the 10,000 pores of the eggshell is remarkably intense. Every second a net of 20 trillion (20,000,000,000,000) oxygen molecules flows into the egg through each pore and 14 trillion molecules of carbon dioxide and 12 trillion molecules of water vapor flow out.'' An egg is quite a center of activity!

Scientists have found that the rate at which gases diffuse through an eggshell is determined by the area and the length of the pores in the shell. The larger the area of the pores, the faster gases can flow through them; but the longer the pores, the slower the gases travel. And the sizes of the pores are no accident-major problems would occur if the pores were too large or too small. The situation is clearly described in [1, p. 47]:


``If the gas conductance is too high, the oxygen requirement of the embryo will be amply met but too much water will be lost, resulting in dehydration. If the gas conductance is too low, the embryo will either suffocate for lack of oxygen, be poisoned by its own carbon dioxide or drown in its own metabolic water. A happy medium must be struck that provides optimal gas pressures in the embryo and ensures a finite loss of water from the egg.''


Another important factor is the width of the shell, which determines the length of the pores. If the shell is too thin, it will not adequately protect the chick inside. On the other hand, if the shell is too thick, it will not allow enough oxygen to reach the chick, as described above.

With all of these parameters to be considered, the design of an appropriate eggshell for a particular type of bird is a challenging engineering problem. The eggshell shows evidence of having been planned by a skilled Designer.


The Inside Story

Even the eggshell, with its precise design, cannot by itself provide for all of the respiratory requirements of the chick that is rapidly growing inside the egg. But in His great wisdom, our Creator has planned some ingenious methods of satisfying these requirements.

A chick needs increasing quantities of oxygen as it grows. The increased demand for oxygen is satisfied by the chorioallantois, a respiratory organ analogous to the placenta of mammals. The chorioallantois begins extending out from the chick embryo on the fifth and sixth days of the twenty-one day gestation period of the chick. It attaches itself to the inner membrane of the eggshell and establishes a network of capillaries that carry oxygen to the chick. By the ninth day, it covers about half of the inner surface of the shell; and by day 12, it completely covers that inner surface.

Meanwhile, as water vapor diffuses out of the egg, it is replaced by air that forms an air cell at the blunt end of the egg. Eventually, the air cell grows to occupy about fifteen percent of the volume inside the egg. This is another detail that Grandma was careful to point out to us as she taught us the chores of the hatchery. Every Friday afternoon, we would remove from the top sections of the incubators the trays of eggs in which the chicks had reached their eighteenth day of development. Shining a bright light on the eggs in a darkened room, we then sorted out any infertile eggs and moved the fertile eggs from their original trays to roomier hatching trays, which we placed in the bottom sections of the incubators in preparation for the following Monday's hatch. Under the light, one notable feature of the fertile eggs was the presence of the large air cell. Grandma would often mention that God had given the chick this special pocket of air.

Why is the air cell important? Conveniently, the air cell serves an essential purpose for the chick when it is almost ready to hatch. On the nineteenth day of its gestation period, the chick penetrates the air cell with its beak. Now its lungs are ready for use, and it exercises them for the first time by breathing the air in the air cell. After about six hours of breathing this air, the chick uses its ``egg tooth'' to make a small hole in the eggshell. At this point, the breathing ``warmup'' provided by the air cell has prepared the chick's lungs for the more strenuous breathing that the chick needs to do in order to break out of the eggshell. Within two more days, the hatching process is complete and the chick uses its lungs to announce its success to all who are within earshot. Its loud cheeps are a shrill testimony to the careful design of both the eggshell and the interior portion of the egg.



When I think about these facts, I am struck by how effectively a simple egg witnesses to the wisdom of our Creator. In Psalm 139:14, David declares, ``I will praise thee; for I am fearfully and wonderfully made: marvellous are thy works; and that my soul knoweth right well.'' The more that we learn about the world around us, the more we can see that everything is ``fearfully and wonderfully made.'' I am reminded also of the first verse of a familiar hymn based on Psalm 19:


``The heav'ns God's glory do declare,


The skies His handiworks teach;


Day after day their speech pours forth,


And knowledge night after night.


There is no speech nor spoken word;


Their voice is never heard.


And yet their voice spreads to all the earth,


Their words to the ends of the world.''

Every aspect of God's creation speaks clearly, shouting His wisdom and glory to all the world. If we have ears to hear, we can live our lives in constant awareness that we are walking continually in His presence.




1.       Hermann Rahn, Amos Ar and Charles V. Paganelli, ``How Bird Eggs Breathe,'' Scientific American 240 (1979), no. 2, pp. 46-55.

Issue 4


File translated from TE X by T TH , version 2.79.
On 11 Nov 2000, 14:33.